Particularly in power electronics, it is often necessary to dissipate the heat loss occurring in an electronic component or a module via a heat dissipation surface in the direction of a heat sink, on which the component or the module is mounted, in order to avoid overheating of the component or of the module.
It is particularly favorable for the heat dissipation surface to make contact over as large an area as possible with a corresponding mounting surface of the heat sink. Owing to unavoidable surface roughness and irregularities, however, the heat dissipation surface and the mounting surface touch only over a part of the maximum possible thermal contact surface, that is to say there are generally many points where the heat dissipation surface and the mounting surface are locally separated from one another. In order to reduce the heat transfer resistance in these regions, a thermal interface material (TIM) which compensates for the existing nonplanarities is conventionally used. Such thermal interface materials are, for example, thermally conductive pastes or thermally conductive sheets.
For heat conduction surfaces measuring at most a few square centimeters, and for relatively low power losses, these measures are normally sufficient. Larger heat dissipation surfaces, such as used for example in semiconductor modules, may however have much greater irregularity than small components. Furthermore, owing to different thermal expansion coefficients of components of the semiconductor module to be cooled, which are connected to one another, larger heat dissipation surfaces may bend to different extents depending on the temperature of components involved.
In such an arrangement, the risk arises that, after the thermal interface material has been applied onto the heat dissipation surface of the semiconductor module, it may inadvertently be smeared and/or contaminated, so that contamination of the surroundings occurs.
In order to achieve a particularly low heat transfer resistance between the semiconductor module and the heat sink, it is also known to apply the thermal interface material as a layer with a predetermined structure, for example with an inhomogeneous thickness and/or in a segmented fashion, onto the heat dissipation surface. However, it is very difficult to produce such a predetermined structure, for which reason it is advantageous for the application of the thermal interface material onto the heat dissipation surface to be carried out at the manufacturer of the semiconductor module, while the mounting of the semiconductor module provided with the thermal interface material on the heat sink takes place at the end customer. This, however, generally requires transport of the semiconductor module provided with the thermal interface material to the end customer, which increases the risk of smearing and/or contamination of the applied thermal interface material.